Your eye care professional may suspect age-related-macular-degeneration (AMD) if you are over age 60 and have had recent changes in your central vision. Dry and wet AMD are detected the same way. To look for signs of the disease, he or she will use eye drops to dilate, or enlarge, your pupils. Dilating the pupils allows your eye care professional to view the back of the eye better.
Early detection of wet AMD can significantly reduce the risk of AMD related vision loss.
To detect AMD before symptoms appear, you should be screened if you meet any of the following criteria:
- Over the age of 60
- Have hypertension or cardiovascular disease
- Smoke cigarettes or other tobacco products
- Have a close relative (sibling, parent, or child) with AMD related vision loss
- Had cataract surgery (replacement of the crystalline lens of the eye with an artificial lens)
- Had significant cumulative light exposure (e.g., airline pilots, boaters, farmers)
AMD is detected during a comprehensive eye exam that includes:
Visual Acuity Testing:
Most of us are familiar with the "big E" eye chart. This visual acuity chart measures how well you see at various distances. From a specified distance, usually 20 feet, your vision care provider will ask you to read aloud progressively smaller rows of capital letters. Progress or further decline of AMD is measured in terms of how many letters you can read on the chart after a period of weeks, months, or years. For example, a person might lose the ability to read 15 letters (three lines) in an 18 month period.
Ophthalmoscopy followed by Slit-Lamp Examination:
Your vision care provider will view your retina using a hand-held, or head-mounted, instrument called an ophthalmoscope. First, special drops will be instilled to dilate your pupils, revealing the internal structures of the eye. After this examination, a slit lamp, which is a high-intensity light source combined with a low-power microscope, will be used to examine the frontal structures of the eye.
A tonometer is a hand-held instrument that measures intraocular pressure (the pressure of fluids inside the eye) after anesthetic (numbing) drops are instilled. This test is performed to rule out glaucoma.
The appearance of wavy, broken, or gray lines on an Amsler grid is a strong indication that you have macular degeneration. An Amsler grid is a simple chart composed of horizontal and vertical black lines on a white background with a black dot at the center. If you have AMD, staring at the center dot will make the grid lines around it appear blurry or distorted. Some people may even see blank spots on the grid. In order to make a definitive diagnosis, however, your vision care provider must look at the retina.
Fluorescein is a dye that's administered intravenously (injected into a vein) and taken up by vessels of the eye, allowing your eye doctor to visualize vessels in your choroid and retina to check for neovascularization and RPE detachment. A similar dye called indocyanine green may also be used to obtain additional information about the vasculature (vessel structure) of your eye. Eye diseases other than AMD can cause abnormal vessel growth, so your vision care provider must assess the extent, type, and location of the new vessels and carefully consider your signs and symptoms in order to diagnose AMD.
Optical Coherence Tomography:
Optical coherence tomography (OCT) is a test that produces high-resolution images of cross-sections of the retina, allowing its thickness to be measured. Areas of thinning may indicate macular degeneration. This test can also show abnormal fluid build-up in and under the retina. OCT works like ultrasound, except that it measures scattered light instead of sound waves.
Understanding Your Diagnosis:
Early detection of AMD is essential to preserving your vision. That's why it's important to learn everything you can about AMD. Arrive for your appointments prepared with notes on your symptoms and ask questions about anything you don't understand. Take an active role in preventing vision loss.